6.5 Medical Imaging Flashcards
(15 cards)
how are x-rays produced
when charged particles are rapidly decelerated (or accelerated) and their kinetic energy is transformed into high frequency photons of electromagnetic radiation
what’s Bremsstrahlung or braking radiation
when radiation is given off by charged particles due to their acceleration
how are gamma rays produced
by radioactive decay or during particle collisions with a mass defect
what are x-rays often referred to in medical imaging and why
soft x-rays as they have energies generally lower than gamma rays
how do x-ray tubes produce x-rays
by accelerating electrons in ahigh voltage electric field then rapidly decelerating them via collisions with a hard metal anode
what metal is usually used for the anode within an xray tube
tungsten
Where and how are electrons emitted from in an X-ray tube
from a heated filament (cathode) into a vacuum tube through thermionic emission
why is a vacuum tube used in an x-ray tube
to prevent electrons from colliding with air molecules before they have enough energy to emit x-rays
What is the role of the external power supply in an X-ray tube
It creates a potential difference between the cathode and anode, giving the electrons up to 200 kV of kinetic energy
What happens when electrons collide with the anode
The electrons decelerate rapidly, and about 1% of their kinetic energy is emitted as X-rays; the rest is lost as heat in the anode
How is heat managed in the X-ray tube’s anode
The anode is either rotated or cooled with circulating water to prevent overheating
Why are X-rays emitted in all directions from the anode
To produce a collimated beam, the vacuum tube has a thinner window where X-rays are allowed to exit in a controlled direction
What is the purpose of a collimator in an X-ray tube
directs the X-rays into a straight, parallel beam to minimize exposure and target specific areas
whats a collimator
a series of metal tubes
